My initial experience of the game was much like the EG review but after just reading some advice on the EASports foum I have cracked it. I have just won 9 games in a row (admittedly on easy) including the Australian Open and, perhaps more significantly, have started to love the experience of playing.

Here are my (borrowed) tips:
1. Use the nunchuk.
2. Treat the left and right sides of the Wiimote as the faces of the racket.
3. Keep the Wiimote still, parallel to the floor and pointing at the television in the couple of seconds between each point in order to allow recalibration to occur.
4. (This is the tip which made all the difference for me) Don't go for a big backswing. In fact, don't turn the Wiimote more than 90 degrees to the left or right when taking a 'back'swing - i.e. don't point it behind you at all.
5. Move the Wiimote up when hitting for topspin, down for slice.

The end result is not at all like real tennis, but it is (a) fun, (b) linked to skill / practice, (c) better than the tennis in Wii Sports.